Synthetic Auxins and Auxin Transport Inhibitors are generally used for controlling broadleaf weeds in grass crops, pastures, and industry. These herbicides include some of the more effective chemicals for perennial broadleaf weed and brush control. These herbicides, also known as plant growth regulators, are readily absorbed through both roots and foliage and translocate by phloem or xylem to meristematic tissue interfering with cell formation that results in abnormal root and shoot growth. The killing action of synthetic auxins is not caused by any single factor but rather by the disruption of several growth processes in susceptible plants. It seems, however, that the primary action of these herbicides is likely to affect cell wall plasticity and nucleic acid metabolism. Synthetic auxins also affect protein synthesis, cell division and growth, and stimulate ethylene evolution, which may in some cases produce the characteristic epinastic symptoms associated with exposure to these herbicides.
Maybe when ethylene is synthesized during senescence,ripening or leaf abscission, this ethylene also inhibits auxin transport. Efflux carrier inhibited by set of compounds calledPHYTOTROPINSPhytotropins include:NPAN-1-napthylphthalamic acidCPDCMF Phytotropins inhibit effluxcarrier protein, thus stimulate IAA uptake (more IAA remains in tissue since itisn't transported out).NPA:inhibitslateral root formation (0.05 uM)inhibitsgravitropic response (>0.05 uM)inhibitsroot elongation (1 uM) NPA binding protein (called NBP=NPA BindingProtein) in cell membrane- Screen Arabidopsis fortransport mutants that interact with NPB.
Growth and Plant Hormones - Biology Online